It is known in the semiconductor device art, particularly the art of MOS (metal-oxide-semiconductor) devices, that nuclear radiation produces undesirable effects on device operation. More specifically, exposure of an MOS capacitor device to gamma rays produces an undesirable shift of the flatband voltage, ordinarily a shift of negative polarity; and exposure of a MOSFET (field effect transistor) device to these gamma rays produces a corresponding undesirable shift in the transistor threshold voltage. Thus, gamma ray dosages of as low as about 10.sup.5 radiation units (rads) ordinarily destroy the device operation of transistor devices integrated in a given monocrystalline silicon semiconductor body, by producing a threshold voltage shift of 100% or more. It therefore would be desirable to have a method for making semiconductor devices less sensitive to nuclear radiation; that is, a method for radiation hardening of these devices.